Semiconductor light emitting device

Abstract

A semiconductor light emitting device includes a multi-quantum-well structure, a first capping layer, a second capping layer, and an electron barrier layer stacked in order. The multi-quantum-well structure includes a plurality of alternately-stacked potential barrier layers and potential well layers. The first capping layer is a semiconductor layer, and the second capping layer is a p-doped semiconductor layer. Each of the first and second capping layers has an aluminum mole fraction larger than that of each of the potential barrier layers, and the aluminum mole fraction of the first capping layer is larger than that of at least a portion of the electron barrier layer. A method for preparing the semiconductor light emitting device is also provided.

What is claimed is: 
     
       1. A semiconductor light emitting device, comprising:
 an n-type semiconductor layer, a multi-quantum-well structure, a first capping layer, a second capping layer, an electron barrier layer, a p-type semiconductor layer, and a p-type contact layer stacked in order, 
 wherein said multi-quantum-well structure includes a plurality of alternately-stacked potential barrier layers and potential well layers; and 
 wherein said first capping layer is one of an undoped semiconductor layer and a p-doped semiconductor layer, said second capping layer being a p-doped semiconductor layer, said second capping layer being directly formed on said first capping layer, 
 wherein each of said first and second capping layers has an aluminum mole fraction larger than that of each of said potential barrier layers, the aluminum mole fraction of said first capping layer being larger than that of at least a portion of said electron barrier layer. 
 
     
     
       2. The semiconductor light emitting device as claimed in  claim 1 , wherein said electron barrier layer is an aluminum gallium nitride (AlGaN)-containing layer having an aluminum mole fraction ranging from 0.02 to 0.25, which is less than that of said first capping layer. 
     
     
       3. The semiconductor light emitting device as claimed in  claim 1 , wherein said electron barrier layer includes a first electron barrier sublayer and a second electron barrier sublayer. 
     
     
       4. The semiconductor light emitting device as claimed in  claim 3 , wherein said first electron barrier sublayer is an aluminum nitride (AlN)-containing sublayer, and said second electron barrier sublayer is an AlGaN-containing sublayer. 
     
     
       5. The semiconductor light emitting device as claimed in  claim 4 , wherein said second electron barrier sublayer has a thickness larger than that of said first electron barrier sublayer. 
     
     
       6. The semiconductor light emitting device as claimed in  claim 4 , wherein said first electron barrier sublayer has an aluminum mole fraction larger than that of said second electron barrier sublayer. 
     
     
       7. The semiconductor light emitting device as claimed in  claim 3 , wherein the aluminum mole fraction of said first capping layer is larger than that of said second electron barrier sublayer. 
     
     
       8. The semiconductor light emitting device as claimed in  claim 1 , wherein said first capping layer is one of an undoped aluminum nitride (AlN) layer and a p-doped AlN layer, and said second capping layer is a p-doped AlGaN layer. 
     
     
       9. The semiconductor light emitting device as claimed in  claim 8 , wherein the aluminum mole fraction of said first capping layer is larger than that of said second capping layer. 
     
     
       10. The semiconductor light emitting device as claimed in  claim 1 , wherein said second capping layer has a thickness larger than that of each of said potential well layers of said multi-quantum-well structure. 
     
     
       11. The semiconductor light emitting device as claimed in  claim 1 , wherein said second capping layer has a p-type doping concentration higher than that of said p-type semiconductor layer and lower than that of said p-type contact layer. 
     
     
       12. The semiconductor light emitting device as claimed in  claim 1 , wherein said second capping layer has a p-type doping concentration between 1×10 19  cm −3  and 5×10 20  cm −3 . 
     
     
       13. The semiconductor light emitting device as claimed in  claim 1 , wherein said second capping layer has a thickness less than 40 nm. 
     
     
       14. The semiconductor light emitting device as claimed in  claim 2 , wherein said second capping layer is an aluminum gallium indium nitride (AlGaInN)-containing layer having an aluminum mole fraction not larger than that of said electron barrier layer. 
     
     
       15. The semiconductor light emitting device as claimed in  claim 3 , wherein said first electron barrier sublayer has a thickness less than that of said second electron barrier sublayer. 
     
     
       16. The semiconductor light emitting device as claimed in  claim 1 , further comprising a growth substrate formed on said n-type semiconductor layer opposite to said multi-quantum-well structure, and a buffer layer formed between said n-type semiconductor layer and said growth substrate, said buffer layer being made from a material selected from the group consisting of AlN, gallium nitride (GaN), AlGaN, aluminum indium gallium nitride (AlInGaN), indium nitride (InN), indium gallium nitride (InGaN), and combinations thereof. 
     
     
       17. The semiconductor light emitting device as claimed in  claim 1 , wherein each of said potential barrier layers is one of an undoped semiconductor layer and an n-doped semiconductor layer. 
     
     
       18. The semiconductor light emitting device as claimed in  claim 1 , wherein said electron barrier layer includes a first electron barrier sublayer, a second electron barrier sublayer, and a third electron barrier sublayer, wherein each of said first and third electron barrier sublayers has an aluminum mole fraction larger than that of said second electron barrier sublayer, and the aluminum mole fraction of said first capping layer is larger than that of said second electron barrier sublayer. 
     
     
       19. The semiconductor light emitting device as claimed in  claim 18 , wherein each of said first and third electron barrier sublayers has a thickness less than that of said second electron barrier sublayer. 
     
     
       20. The semiconductor light emitting device as claimed in  claim 19 , wherein at least one of said first and third electron barrier sublayers has a thickness less than 5 nm.